1. Field of the Invention
The instant disclosure relates to an illumination device, and more particularly, to an illumination device with a progressive-type design for generating a uniform light-emitting source having the same light-emitting intensity.
2. Description of Related Art
Light-emitting diode (LED) has been outstanding in energy-saving lighting with its features of small size, long device lifetime, high durability, environmental friendliness, and low power consumption. Of all the LEDs, white light LED (or LED with compound lights) combines two or more monochromatic lights and has been widely used in indicating lamps and display devices in information technology, communications, and consumer electronics products. In addition to improving the light emission efficiency, the unevenness of lights from the LED also requires an urgent solution in the study of compound LED and lamp.
To solve the unevenness issue, a prior art with coating phosphor onto the surface of the LED chip has been proposed. However, another problem, such as limited chip type, high cost, low light emission efficiency or narrow light angle is encountered.